In the games, the cities only need four or five important buildings; A Pokemon Centre, A Pokemon Mart, a gym, a Contest Hall and perhaps a building with important relavance to the plot (i.e. Silph Co, Galactic Hideout, etc...)
All the houses are just there to make things more city-like. What's the point of having some overly large city in a game with fifty odd houses?
In the anime, the regions are so much more bigger than the ones in the games. The anime is meant to represent real life and, if you were to compare a region to a country, would have more than just ten or eleven towns/cities. Really, there would be hundreds of towns. Great Britain is a small island but still has so many cities and towns. Imagine how many Sinnoh or Hoenn would have.
Everything about the movies are special; the people, the Pokemon, the scenario and the location. Also, what would sound more important, Dialga and Palkia fighting in Cherrygrove City (for example) or Alamos?